Tick… tick… tick… DING. That was the sound of season 5 running out. Showtime’s serial-killer drama Dexter wrapped up its fifth year on Sunday night with a knife in the chest—literally and figuratively—while weaving in a twist or two. [SPOILER ALERT: Do not proceed if you haven’t watched the season finale.] While “The Big One” didn’t pack the shock of last year’s Trinity-Rita send-off, there’s ample action to analyze—and character motivations to assess. Herewith, Dexter executive producer Sara Colleton sheds light on Lumen’s departure, Deb’s big decision, Dexter’s new outlook, and much more….

EW: Two years in a row, Dexter (Michael C. Hall) has lost the woman he loves, albeit in two very different ways. Was it always the intention to have this season end with Lumen (Julia Stiles) alive, but not with Dexter?
SARA COLLETON: From the very beginning we knew that Lumen would leave Dexter. In his season-long journey toward atonement [for his part in Rita’s death], this woman tumbles into his life and inadvertently becomes the way in which he does achieve atonement. But along the way this miracle happens—something that Dexter never thought would be possible in his life—he finds a soul mate…. Once she goes from victim to avenging angel, he realizes that she is the woman who has the kind of strength of resolve that Dexter has, and he exposes himself completely to her. Instead of turning away in horror, she empathizes and is so grateful to him for his courage and support. Their respective traumas have created this bond. So it’s devastating for Dexter to lose her, and he has never wanted anything before like this. But at the same time there’s something so incredibly direct about Lumen that when she tells him why she has to leave, it makes perfect sense to him. He understands that her dark passenger has left, that her need for vengeance has been quenched, and that he can never escape this, this is who he is, and he needs to let her go. As he said, “I will carry your darkness with mine.”

That might be the most romantic thing Dexter has ever said.
Oh my God, it’s so romantic. But he accepts that it’s his punishment. And at Harrison’s first birthday party, Dexter has realized with ruefulness and irony that the circle has come full and that he has paid his price—and the price has been one true love. He has let Lumen go out into the world. But she has left behind two very real gifts, two pieces of knowledge that leave Dexter in a place he’s never been before, which is the knowledge that he can be seen and that he can be loved. The other gift is that Harrison does not have to be doomed to a life of darkness, even though Dexter reproduces his own making, if you will, by being responsible for his son witnessing his mother’s bloody death. By witnessing what Lumen went through, Dexter realizes that you can vanquish darkness and go on to a normal life.

Yet with that optimism comes some dark resignation. As he says: “But wishes, of course, are for children.”
It’s rueful, it’s ironic, but it’s a healed Dexter who says, “I am who I am.” More than ever he realizes who he is, but not with an absolute sense of bleakness. He felt what it was like to be seen, to be loved, truly. That is a huge thing that he’s going to hold on to.

Is the door open for Lumen to return?
She’s alive, so therefore the door is, of course, open.

Are you leaning to doing next season with multiple villains again, or returning to a single season-long adversary story?
We’re so grateful that our fans stayed with us and realized, “Even though they’re changing some things, they’re not changing the core of what the show is.” We can go back to the season-long adversary, we can go back to multiple adversaries, or we can open it up to some new way of plotting out season [6], which we haven’t thought of yet.

A huge moment for Deb: She chooses not to pull back the curtain to discover the identity of Victim 13 and her partner, allowing Lumen and Dexter to go free. Why did you decide to go that way with the story?
Deb has had a really interesting growth over the past five years. If you remember her from year 1, her energy was all over the place and she was coltish and insecure—this delightful unfocused character who slowly over the years has learned to focus all of that energy and she has become a formidable detective. But part of becoming a detective and pursuing the dark side is an awareness that anyone who takes a walk on the wild side never comes back all the way. What may have started out as a rigid sense of what’s right and wrong—what’s good and evil—starts to turn into a bit of gray. And when Deb finally brings down Carlos Fuentes earlier in the season, she’s surprised that she feels nothing—and is intrigued by that sensation. And one of the most subtle conversations between Dexter and his sister takes place over a beer in Dexter’s apartment when she’s going on about how she didn’t feel anything, and Dexter gives her this look and goes, “Dad once told me there are people who deserve to die.” And she looks at him and goes, ‘Do you think there are people that deserve to die?” It’s this moment where Dexter has floated out this little trial balloon. So you see Deb starting to make that turn. And based on her experience with Rudy and in episode 10 when she sees all of those [Barrel Girl] tapes—it’s traumatizing yet strengthening for her—she comes up with the vigilante theory. When she finally gets to the camp and realizes that she has stumbled upon “13” and her helpmate, it’s not until the very end of her speech where she makes that change. And Jennifer Carpenter did a brilliant piece of acting because the character doesn’t know until that very moment that she’s going to do something. It’s a huge, defining moment for Deb. That’s a new Deb who says, “The place is going to be crawling with police in an hour,” and sails up the stairs and goes to Quinn and says, “I don’t care what happened—I love you.” It’s wonderful—and it also opens the door because eventually, some season is going to have to deal with Deb finding out about Dexter.

Didn’t part of you wonder if her curiosity would have won out in that situation?But that’s what interesting because it shows a maturation in that impulse control. One of the things that Jennifer [Carpenter] and I talked about was the levels that Deb would have to go through in that one scene to get to that moment. Her first instinct would be, “I’ve worked too hard. Part the curtain for a minute, take a look.” But Deb being Deb, if she parts the curtains, she can’t let them go. So it’s a big choice she has to live with, never knowing that and letting them go.

Will we have to wait until the end game for Deb to finally find out the truth about Dexter?
[Or] it could be midway to the end game. We really want to figure out how long we want the show to run, so that we [can have] an end game. I will not let this show end with a whimper—it has to end with a bang…. What’s interesting is that we’ve laid the seeds in her character for a more nuanced reaction, so that whatever way we take, our audience goes, “Okay, that feels right,” rather than, “What???”

Let’s talk about the twisted self-help guru Jordan Chase, who, as he is about to die, seemed to take genuine pride that he had motivated Lumen and Dexter….
And he completely believes in the transformation from Eugene Greer to Jordan Chase—as he lay dying, that is still his greatest accomplishment…. The audience knows before Dexter knows that he’s a bad guy, and his advice to Dexter is so true and sincere that you have to constantly remind yourself that he’s a bad guy. And then his psychosis is slowly revealed, and once it is, he’s unhinged. [Jonny Lee Miller] plays it full-throttle in a way that’s such a pleasure to witness. I thought he gave an amazing ballsy performance.

When exactly did Dexter stash the knife that he used on Jordan?
It was before he got into the car—he realized that Jordan would know he was coming for him and would have a surprise prepared for him, so Dexter prepared himself for the worst possible scenario. When Harry says, “Be prepared,” and Dexter says, “Could you just trust me for once?,” he’s already had that knife hidden on his body in anticipation of something going wrong.

Looking back at season 5, what are you most proud of?
I think we pulled off Lumen. Society holds women up to a different standard of behavior, so having a woman who wanted to avenge what was done to her and is single-minded about it was a very hard thing to pull off. It’s a thorny, hard character that is not feminine. And yet Julia played it so real that you care about her, and you end up rooting for her and for this odd romance.

And what didn’t work as well as you had hoped?
One character that we didn’t have as much time to explore is the nanny [Sonia, played by Maria Doyle Kennedy]. But that could be something very interesting for next year. As Deb said, “Maybe I should call Interpol, because why this overqualified nurse from Ireland wanting to take this low-level job?” Sonia was able to call Dexter on his s—. She was absolutely fearless in dealing with Dexter. But we had so much going on that we could never really explore that character and that was a regret.

It’s funny you say that because some fans wondered if something sinister was going with Sonia, or if you were toying with us and she was just a red herring.
No, we always want to bring in characters with as much dimension as possible. If Harrison is going to have a nanny, let’s [make her] the most interesting character. And then we got [Maria], Catherine of Aragon from The Tudors. She is a wonderful actress. The season became so complicated with so many characters because we were breaking form a bit that we never got to explore hers to the fullest…. I hope we do so next year, because there’s a great deal of potential there.

Speaking of loose ends, will we return to the Kyle Butler story line?
Kyle Butler—and Jonah [Brando Eaton]—is still a hanging chad. When Quinn shows him a picture of Dexter and says, “Is this Kyle Butler,” Jonah’s first response is not, “Yeah, that’s the guy.” He’s protecting Dexter. This is a door that can be reopened. Lumen being alive is a hanging chad. Dexter does not drop the dime on Quinn [Desmond Harrington]. I love the fact that Dexter decides to again flout the Harry law, which is: Don’t get caught. It could have been a dead cert to put Quinn away, and yet, because he is in the flush of first love, he wants his sister to be happy so he gives Quinn a free pass.

What’s one guarantee you can make about next season?
Hmmm… Deb will learn Spanish, I think Harrison will be seeing his second birthday, and Dexter will still be enjoying the Slice of Life.